Watch pallet lever having integral projection determining swing

ABSTRACT

A watch pallet lever formed of sheet material has an integral tab bent up to form a projection engageable with opposite edges of a notch or opening in a bridge plate to define the operational region of the pallet lever.

United States Patent 1 Kurita 1 May 8, 1973 [54] WATCH PALLET LEVER HAVING [56] References Cited INTEGRAL PROJECTION DETERMINING SWING UNITED STATES PATENTS [75] Inventor: @El mTag k Japan 257.727 5/1882 Lane ..58/l2l R [73] Assignee: Kabushiki Kaisha Suwa Seikosha, Primary ExaminerRichard B. Wilkinson Tokyo, Japan Assistant ExaminerStanley A. Wal Filed: Dec. 1971 Attorney-Robert E. Burns et al. [21] Appl. No.: 212,495 [57] ABSTRACT A watch pallet lever formed of sheet material has an [30] Forei n A lication Pri it D t integral tab bent up to form a projection engageable with opposite edges of a notch or opening in a bridge 1360.28, 1970 Japan", ..45/l32724 plate to define the Operational region of the pallet lever. [52] U.S. Cl. ....S8/116 R [51] Int. Cl. ..G04b 15/00 7 Claims, 2 Drawing Figures [58] Field of Search ..58/1l6 R, 28 R, 121 R, 58/122; 74/l.5

. 7 3b 2 W lll I A 5 \\\\\\\i|gp\\\\\\|i| llllll-lllll WATCH PALLET LEVER HAVING INTEGRAL PROJECTION DETERMINING SWING The present invention relates to lever escapements for watches and particularly to the pallet levers of such escapements.

in a lever escapement, the pallet lever is conventionally a three arm T-shaped lever pivotally mounted between support plates of the watch at the conjunction of the three arms. Two shorter arms approximately in line with one another carry respectively entrance and exit pallet stones engageable with the teeth of an escape wheel to control the intermittent rotary movement of the escape wheel and thereby the movement of the watch. A third, longer arm extends approximately perpendicular to the other two and is provided at its free end with a fork which is engageable by the ruby pin on the balance wheel to oscillate the pallet lever and thereby intermittently release the escape wheel for step-by-step movement. In a lever escapement it is necessary to define the amplitude and angular position of the operational region of the pallet lever. Otherwise the accuracy and reliability of the watch are adversely affected. Heretofore it has been customary to determine the operational region of the pallet lever by means of small pins, called banking pins, which project form one of the plates by which the pallet lever is pivotally supported and are engageable respectively with opposite edges of the longer arm of the pallet lever near the fork to limit its oscillatory movement. In order to mount the banking pin, it is necessary to drill two holes in exactly the right locations in the plate to receive the pins. This is a precision operation which increases the cost of manufacture of the watch. If the holes are not accurately positioned, the watch does not run accurately. The insertion and securing of the banking pins in the holes, for example by soldering, involves additional operations in the manufacture of the watch. Moreover, if the plate is thin which is usually the case in small watches it does not properly support the banking pins to withstand the repeated engagement of the pallet lever. Hence, the use of banking pins leaves much to be desired as a means of defining the operational region of the pallel lever of the lever escapement of a watch.

It is an object of the present invention to provide improved means for determining the operational region of the pallet lever of the lever escapement of a watch which not only improves the accuracy and reliability of the watch but also reduces the number of parts and assembly operations and thereby reduces the cost of manufacture of the watch. ln accordance with the invention, the operational region of the pallet lever is determined by a projection on the pallet lever that is integral with the lever itself and is engageable with the edge ofa notch or other opening provided in one of the plates pivotally supporting the pallet lever. When the lever is formed of sheet metal, the projection is conveniently formed as a tab which is partially severed and bent up from the material of the lever. This can conveniently be done in the same operation as stamping the lever from strip or sheet stock. Hence, no additional parts and no additional assembling operations are required to provide means for determining the operational region of the pallet lever in accordance with the present invention.

The nature and advantages of the invention will be more fully understood from the following description ofa preferred embodiment shown by way of example in the accompanying drawing, in which:

FIG. 1 is a schematic plan view ofa pallet lever and associated parts of a lever escapement of a watch in accordance with the present invention, and

FIG. 2 is a schematic section taken on the line 2-2 in FIG. 1.

As illustrated in the drawings, the pallet lever 3 of the lever escapement ofa watch is pivotally supported by a shaft 4 between two support plates 1 and 2 of a watch movement. The support plates 1 and 2 are spaced from one another in conventional manner, for example by posts or pillars 6 to which the plates are secured by screws 6a. The pallet lever is shown as a three arm T- shaped lever comprising two shorter arms 3c and 3d approximately in line with one another and a longer arm 3a approximately perpendicular to the other two arms, the pivot shaft 4 being located at the conjunction of the three arms. The two shorter arms carry respectively an entrance pallet stone 5a and an exit pallet stone 5b engageable with the teeth of an escape wheel (not shown) to control the intermittent release of the escape wheel in usual manner. At the free end of the longer arm 3a there is provided a fork 3e which is engageable in usual manner by the ruby pin ofa balance wheel (not shown) to oscillate the pallet lever.

In accordance with the present invention, an integral projection 3b provided on the longer arm of the pallet lever 3 near the fork 3e is engageable with the opposite edges 2a and 2b ofa notch or recess 2c provided in one of the support plates 2 to determine the operational region of the pallet lever. As illustrated in the drawing, the pallet lever is formed of sheet stock and the projection 3b is formed as an integral tab which is defined by a U-shaped cut and bent up out of the plane of the lever at an angle so that the tip of the tab extends up into the plane of the support plate 2. The projection 3b is located centrally of the width of the lever arm 3a and is hence symmetrical with respect to the section line 2-2 which defines the longitudinal axis of the arm 3a. The tab comprising the projection 3b is conveniently formed in the same operation as the stamping of the pallet lever 3 from strip or sheet stock. Hence the projection 3a does not increase the weight or moment of inertia of the pallet lever and, moreover, does not increase the operations required for its manufacture and assembly.

As abutments engageable by the projection 3b to limit the oscillation of the pallet lever 3 are provided by the opposite edges 2a and 2b of an opening 20 in one of the support plates 2 of the watch movement, no additional parts such as banking pins are required. According to the construction of the watch movement, the plate 2 may be a front or back plate or a bridge pivotally supporting one end of the shaft 4 of the pallet lever 3. In accordance with the present invention, it can be made of thin stock having only such thickness and strength as are required for the pivotal support of the pallet lever and such other watch parts, for example the balance wheel and escape wheel, as are disposed between tlie plates 1 and 2. As the forces applied to the plate 2 by engagement of the projection 3b of the pallet lever 3 with the opposite edges 2a and 2b of the opening 2c are in the plane of the. plate 2, no additional thickness of the plate is required by reason of the function of determining the operational region of the pallet lever. Moreover, since the opening 2c can be formed in the same operation as stamping the plate 2 from sheet stock, no additional manufacturing or assembling steps are required. As the opening 20 is formed by the same die that forms the plate 2, accurate positioning of the opening is assured. Instead of being in the form of an open notch or recess as shown in FIG. 1, the opening 20 can be in the form ofa hole in the support plate.

It will thus be seen that the novel construction in accordance with the present invention assures precise definition of the operational region of the pallet lever and thereby contributes to the accuracy of the watch. Moreover, it eliminates the cost of making and assembling banking pins to limit the swing of the pallet lever, while at the sanie time providing more accurate control of the oscillation of the pallet lever. Thus the quality and precision of the timepiece are improved while reducing its cost of manufacture.

What I claim and-desire to secure by Letters Patent 1. In a watch having parallel spaced support plates and an escape wheel, balance wheel and'pallet lever pivotally supported between said plates, said pallet lever comprising first and second arms extending oppositely from the pivot of said lever and a longer third arm extending approximately perpendicularly to a line connecting said first and second arms, said first and secondarms being engageable with teeth of said escape wheel and said third arm cooperating with said balance wheel to oscillate the pallet lever, the improvement comprising a projection integral with said pallet lever comprising a portion of said third arm bent up into the plane of one of said plates and received in an opening in said one plate, said projection being engageable with the edge of said opening to position the operational region of said pallet lever.

2. In a watch according to claim 1, said pallet lever being of sheet material and said projection comprising a tab partially severed from and bent up out of the plane of said sheet material.

3. In a watch according to claim 2, said tab being defined by a U-shaped cut in said sheet material, said tab being near the fork of said pallet.

4. In a watch according to claim 3, said tab being bent up at that side of said U-shaped cut nearest the pivot of said lever.

5. In a watch according to claim 2, said projection being bent up along a line extending transversely to said third arm. r v

6. In a watch according to claim 5, said tab being bent up at an angle less than to the plane of said pallet lever.

7. In a watch according to claim 1, said opening comprising a recess in an edge of said one support plate. 

1. In a watch having parallel spaced support plates and an escape wheel, balance wheel and pallet lever pivotally supported between said plates, said pallet lever comprising first and second arms extending oppositely from the pivot of said lever and a longer third arm extending approximately perpendicularly to a line connecting said first and second arms, said first and second arms being engageable with teeth of said escape wheel and said third arm cooperating with said balance wheel to oscillate the pallet lever, the improvement comprising a projection integral with said pallet lever comprising a portion of said third arm bent up into the plane of one of said plates and received in an opening in said one plate, said projection being engageable with the edge of said opening to position the operational region of said pallet lever.
 2. In a watch according to claim 1, said pallet lever being of sheet material and said projection comprising a tab partially severed from and bent up out of the plane of said sheet material.
 3. In a watch according to claim 2, said tab being defined by a U-shaped cut in said sheet material, said tab being near the fork of said pallet.
 4. In a watch according to claim 3, said tab being bent up at that side of said U-shaped cut nearest the pivot of said lever.
 5. In a watch according to claim 2, said projection being bent up along a line extending transversely to said third arm.
 6. In a watch according to claim 5, said tab being bent up at an angle less than 90* to the plane of said pallet lever.
 7. In a watch according to claim 1, said opening comprising a recess in an edge of said one support plate. 